Laminated paper product



Jayne 7- I f R. A. .TEFl-EN 3,

LAIINATED PAPER PRODUCT Filed Aug. 2, 1944 mmwmmdmim" 7 ca v INVENTOR Patented June 24, 1941 Raymond A. Steflen, Hamilton, Ohiotascignor to The Champion Paper and Fibre, Company, Hamilton, Ohio, a corporation oi Ohio Application August 2, 1944, Serial No. 541,809

Claims. (01. 1541-50) This invention relates to laminated moistureproof paper products such as asphalt-laminated papers and the like.

Asphalt and many of the wax products used as moistureproofing laminants apparently contain a modicum of free oily material which, though dimcult if not impossible to remove and apparently necessary to impart to the laminant the required moistureproofing and/or plastic and adhesive properties, nevertheless tends to bleed out of the laminant and discolor the fibrous paper web, if allowed to stand, particularly at the higher temperatures-to which such products are sometimes exposed.

The primary object of the present invention is accordingly to provide in'laminated paper made with moistureproofiing laminants which contain a modicum of free oily material,- means for inhibiting the tendency of the oily material to bleed into and discolor the fibrous web.

I have now discovered that it the fibrous paper webs used are, prior to contact with the laminant; coated on the surface which subsequently contacts the laminant, with a suitable coating composition, the undesirable penetration of the oily material into the fibrous web can be'largely inhibitecll The type of coating which I find useful for this purpose resembles incertain respects some of the coatings applied to paper to enhance its value for high grade printing. While oil-imperviousness might seem to be the property needed in coatings for this purpose, I have found that absorbency, above that common in the surface of coated printing papers, renders the coatings effective in inhibiting penetration of the oily material into the fibrous web. Further, the coating need not be smooth as is required for printing, and it need not adhere to the paper with the strength frequently required in the printing operation though it obviously must have sufficient strength to prevent dusting or fiaking ofi in the laminating process. Accordingly I prefer that the pigment content of the coating comprise a material proportion of a highly oil-absorbent pigment such as, for example, precipitated calcium carbonate. The adhesive used may be a usual paper coating adhesive such as starch or casein. The amount required, as is well understood in the paper coating art, depends on the nature and particle size, etc., of the pigment as well as on the adhesive itself. Because oi the lower requirements as to strength, and the desire for absorbency in the coating, I ordinarily find it desirable to use only one-half to threebe used with the same pigment in the manufacture of coated printing paper. The'coating may be applied to the paper in any usual manner, but calendaring or supercalendering, after coating,

5 such as is usual with coated paper for printing purposes is advantageously either completely omitted or held to a minimum. The dry weight of the coating applied, depending on the nature of the coating and of the laminant, is advantageously from about one-third the weight of the laminant to slightly over the weight of'the lam- .inant, depending on the absorbency of the coating and theamount of free oil in the laminant, this weight of coating being advantageously di- -vided between the paper webs on opposite sides of the laminant.

Contrary to expectations, it was found that when coating made with the high absorbency described was placed adjacent the oil-containing laminant it served as a bar, substantially preventing deleterious penetration of the oil into the fibrous web. In the case of laminated sheets in actual use such absorbent coatings have been frequently found to constitute a more effective bar than more costly oil-impervious films. Theoil-absorbent coatings appear -to hold the oil against the attractive forces of the likewise. absorbent fibrous web, and this holding capacity appears to be substantially unaffected by pinholes or cracks in the coating. An oil-impervious layer on the other handdepends upon continuity for its effectiveness as a bar. Pinholes and cracks, such for example as sometimes occur when laminated sheets are creased on a packaging me.-

chine, constitute leaks through which the oily material bleeds freely into the fibrous web and spreads laterally, causing unsightly spots and streaks in the package.

The invention will be further described with 40 reference to the accompanying drawing in which Fig. 1 represents, more or less diagrammatically, a highly magnified cross section of a laminated paper web made in accordance with the invention, and- Fig. 2 is a like drawing of a similar web in which the oil-absorbent coating is'carried on only one of the paper laminae.

Referring first to Fig. l, the paper web 3 is composed 'of' fibers I felted together in random arrangement as in usual paper making practice. 7 The upper surface of web .3 is covered by a coating 5 which serves to fill in the surface depressions and protect the surface fibers from contact with the laminant. This coating is, as already described. composed of pigment which is held tofourths as much of any given adhesive as would gether and to the paper with adhesive. The ada the form of a layer hesive is preferably present in materially smaller proportion than that in which the same adhesive would normally be used with the same pigment in the art of coating paper to enhance its value as a base for fine printing.

Over the surface of the coating layer is a layer 6 of moisture proofing laminant containing a modicum of free oily material. Over and in contact with the moisture proofing layer 8 is the coating layer 1, which covers and fills the de pressions in the surface of, the paper web 8 which is composed of fibers 9 felted together in the same manner as the fibers 4 forming web 3.

An oily material which may bleed out of the layer 6 due to prolonged exposure, particularly at elevated temperatures, first enters the coating layers 5 and/or 1. Though the fibrous paper web will absorb oil with great avidity, the coating material appears to have a materially greater ailinity for oil than does the paper web, so that the coating, if sufiicient in amount relative to the amount of free oil, holds the oil and largely prevents it from soaking into and discoloring the fibrous web.

' In the laminated web illustrated in Fig. ,2 the coating material, instead of being divided between the two paper webs, is all concentratedon the surface of the web l3, composed of fibers I l, in I5. On top of this is the layer l8 of oil-containing moisture proofing composition. Laminated therewith is -'the uncoated layer [8 of paper formed of the felted fibers I9. In this case the moisture proofing laminant itself fills the surface depressions in the paper web I8. However, in spite of this direct and intimate contact of the oil-containing laminant with the absorbent web l8, its contact on the other side with the more highly absorbent coating layer l5 apparently results in movement of the oily material towards and into the coating layer l5 so that only a small proportion of the oil bleeds into the paper web I 8. Accordingly the degree of discoloration of web I8 is so slight that it is, in general, not found to be objectionable, though the structure illustrated in Fig. 1 is considered preferable in most cases.

When in the present specification and claims the coating material is defined as being more oilabsorbent or having oil-absorbency greater than that of the fibrous paper web, it is to be understood as meaning that the coating material has a greater aflinity for oil than does the paper, in the sense that it will absorb and retain oil in opposition to the oil absorbing tendencies of the paper web.

The invention will be more clearly understood from the following examples which illustrate its application in actual practice.

Example 1.A paper web weighing 40 pounds per ream (500 sheets 25 x 38' was coated on the papermaking machine with 5 pounds dry weight per ream of a coating composed of about 20 parts of finely precipitated calcium carbonate, 80 parts of china clay, and 20 parts of starch, on the dry basis. Thiswas given no more calendering on the paper machine than was necessary to impart shipping, and storage, and even after prolongef exposure to temperatures of 120 R, there wa: no objectionable discoloration, even at the folds to indicate bleeding of oily material into the fibrous webs.

Example 2. In this case a paper web weighing 23 pounds per ream was coated with 5 pounds per ream dry weight of coating composed of 50 parts of finely. precipitated the dry basis.' This was given Just sufiicient calendering on the paper machine to impart the necessary flatness to the sheet and received no supercalendering whatever. Over this coating was applied a layer of 11 pounds per ream of asphalt. Onto this layer of asphalt before it became hardened and non-aclhesive-was pressed the coated surface of a second web of paper, identical with the first, to form a laminated sheet weighing about 67 pounds per ream. In use this, like the other, showed no objectionable discoloration even at the folds, in spite of its lighter weight, even after prolonged exposure to temperatures of 120 F.

Example 3.In this case the paper used weighed about 24 pounds per ream. To one surface of this paper was applied a coating composed of about 20 parts starch, 50 parts clay, and 50 parts calcium carbonate giving the coated sheet a weight of of this coating was applied a substantially uniform continuous layer of about 12 pounds of a in refers to the desired flatness to the sheet, and received no supercalendering whatever. Over this coating was applied a layer of about 12 pounds per ream of asphalt. Onto this layer of asphalt, before it became hardened and non-adhesive, was pressed a second layer of paper weighing 30 pounds per ream. The resulting laminated sheet was used in a usual type of wrapping machine, as a protective wrapper for cigarettes. After handling,

moistureproofing composition containing a petroleum wax with a modicum of residual oil. A second paper web like the first was then laminated therewith with the moistureproofing layer. In use, this product, like the others showed no evidence of deleterious penetration of oil into the fibrous webs or objectionable discoloration of the webs thereby.

The term moistureproof paper product" herea product composed of at least one fibrous paper layer combined with a moistureproofing agent, i. e. an agent which retards the passage of moisture through the web from an area of higher to one of lower humidity. The product itself may or may not resist the action of, or penetration by, water in the liquid state.

When a coating layer separating a layer of paper from an oil-containing laminant is herein defined as oil-absorbent, it is to be understood to possess oil-absorbency recognizable, by one skilled in the coated printing-paper art, as at least as great as that required in printing paper to meet the common requirement for the absorption of printing ink before it dries by oxidation.

I claim:

1. In a laminated paper product comprising at least one fibrous paper layer and a layer of moistureproofing material containing a modicum of free oily material, a layer of paper coating composition composed primarily of adhesive and mineral filler in proportion more oil-absorbent than said paper layer, separating said moistureproofing layer from said fibrous paper layer.

2. In combination, a fibrous paper web, a moisture-proofing layer containing a modicum of free oily material, and an oil absorbent layer between said paper web and said moisture-proofing layer, for inhibiting penetration of said oily material into said fibrous web.

3. A laminated moisture-proof paper product comprising: two layers of paper; a moistureabout 28 pounds per ream. On top the coated side contacting to render said layer j; i5 prooflnglayer. containing a modicum of. free oily material. between said layers of paper; and

a layer of oil-absorbent paper-coating material,

proofing layer, containing a modicum or tree oily material, between said layers or paper; and a layer of oil-absorbent paper-coating material between said moistureprooting layer and at least one of said layers of paper, said coating material being composed primarily of mineral pigment including a substantial proportion of precipitated calcium carbonate with sumcient adhesive to render the material coherent.

aaaaoas I 5. .A laminatedimoistureprooi paper product comprising: two layers of paper; a moistureproofing layer of asphaltic material between said layers ot'paper; and a layer of oil-absorbent paper-coating material'between said moistureprooflng layer and at least one of said layers of paper, for inhibiting penetration of oily material from the asphaltinto the paper.

1 RAYMOND A. S'IEF'FEN.

' REFERENCES cr'rnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Pennell Mar. 3, 1942 

